Unnamed Occurrence (ARDF - SR213; near Falling Glacier), Prince William Sound District, Valdez-Cordova Borough, Alaska, USA
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Geology: The occurrence consists of an iron-stained, laminated, siliceous mudstone that is locally cut by quart-feldspar veinlets near a granite contact. Traces of chalcopyrite and as much as 2 percent pyrite occur as disseminations and fracture fillings in the mudstone (Kurtak and Jeske, 1986). The mudstone is Orca Group of early Teriary age (Nelson and others, 1985). The granite belongs to the informally named Nellie Juan granite, which has been dated as 35.5 +/-0.9 my old (Lanphere, 1966). One random chip sample across siliceous mudstone and quartz-feldspar veinlets contained 96 ppm copper (Kurtak and Jeske, 1986). A sample collected by Tysdal (1978 [MF-880-A]) contained 300 ppm chromite, 85 ppm copper, 100 ppm nickel, 50 ppm tin, and 90 ppm zinc.
Workings: One random chip sample across siliceous mudstone and quartz-feldspar veinlets contained 96 ppm copper (Kurtak and Jeske, 1986). A sample collected by Tysdal (1978 [MF-880-A]) contained 300 ppm chromite, 85 ppm copper, 100 ppm nickel, 50 ppm tin, and 90 ppm zinc. No workings or improvements are reported.
Age: Tertiary or younger; the mineralization is in rocks of the Orca Group of Tertiary age.
Alteration: The mudstone is iron-stained.
Commodities (Major) - Cu; (Minor) - Cr, Ni, Sn, Zn
Development Status: None
Deposit Model: Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral List
4 entries listed. 3 valid minerals.
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References
Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 1984, Mineral occurrences in the Chugach National Forest, southcentral Alaska: U.S. Bureau of Mines Mineral Land Assessment 5-84, 218 p., 2 sheets, scale 1:250,000. Kurtak, J.M., and Jeske, R.E., 1986, Mineral investigations in the Chugach National Forest, Alaska (Islands area): U.S. Bureau of Mines Open-File Report 54-86, 302 p., 1 sheet. Lanphere, M.A., 1966, Potassium-argon ages in Tertiary plutons in Prince Williams Sound region, Alaska, in Geological Survey Research 1966: U.S. Geological Survey Professional Paper 550-D, p. D195-D198. Nelson, S.W., Dumoulin, J. A., and Miller, M.L., 1985, Geologic map of the Chugach National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1645-B, 16 p., 1 sheet, scale 1:250,000. Tysdal, R.G., 1978, Mines, prospects, and occurrences map of the Seward and Blying Sound quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-880-A, 2 sheets, scale 1:250,000.